Hydraulic press



June 13, 1939. R. w. DlNZL 2,161,804

HYDRAUL IC PRES 5 Filed NOV. 9, 1935 INVENTQR Z W D/hZ/ Patented June 13.1939 v Richard w. mm, Narbertli, Pa., assignor to Baldwin-Sonthwark Corporation, a corporation of Delaware Application November 9, 1935, Serial No. 49,050

IClaim.

This invention relates generally to hydraulic presses and more particularly to an improved control system therefor. Itis an object of my invention to provide an improved control system for a hydraulic press whereby a positive variable displacement uni-directional discharge pump may be efi'ectively and efllciently employed to supply operating fluid alternatively to a main operating cylinder or to pull-back cylinders. A further object is to provide improved control means for the pump toinsure gradual acceleration and deceleration of the press movements.

Another object is to. provide improved means for preventing the movable platen from falling in the event that power for the pump'motor should fail- A stilhfurther object is to provide an improved control system adapted to accomplish all of. the foregoing objects, as well as others, in a manner which is simple and economical in construction, operation and maintenance insofar as is permissible with the character of subject matter herein disclosed.

Other objects and advantages will be more apparent to those skilled in the art from the following description of the accompanying drawadjusting the pump stroke in accordance with platen movement.

In the particular embodiments of the invention, such as are disclosed herein merely for the purpose of illustrating certain specific forms among possible others that the invention might take in practice, I have diagrammatically shown a hydraulic press having a lower stationary platen I and an upper movable platen 2 actuated by a ram 3 in a main cylinder 4. Pull-back rams and cylinders 5 may be arranged in any suitable manner for returning platen 2 to its upper position. A usual filling tank 6 is adapted to have free communication with main cylinder I u pon opening of a filling valve I which is normally urged to its closed position by a spring whereby filling liquid under relatively small air pressure may'openthe valve during initial down move.- ment of ram 3. A pilot ram and cylinder 8 is I adapted to be supplied with fluid pressure to open the filling valve during return movement of the platen.

To initiate down movement of the press, a manually operable pivoted lever I0 is pressed down against the action of a spring II and held 5, by a pivoted latch l2 as shown in Fig. 1. A control rod I3 is thereby moved down with lever ill to shift a four-way manual 'control valve, generally indicated at M, to the right shown in Fig.

I, Thereupon fluid from a variable positive dis- 1o placement pump I5 having uni-directional discharge, preferably of the Hele-Shaw type-as disclosed in Patent No. 1',250,170, to Hele-Shaw et al., is supplied through a discharge pipe l6, check valve l1 and a pipe Hi to main cylinder 4. Also 15 fluid is drawn from pull-back cylinders 5 through a pipe 20, valve l4 and pump-suction pipe 2| to the inlet of pump 15. Exhaust of draw-back fluid permits platen 2 and ram 3 to lower by gravity during which time filling fluid from so tank 6 opens filling valve 1 to admit low pressure fluid to the main cylinder. When the platen engages the work, pump pressure builds up in the main cylinder and accordingly closes the filling valve thereby to continuethe pressing stroke. 25

The main vcylinder pressure is transmitted through a pipe 22 and upon reaching a prede-' termined value raises a' plunger 23 normally urged downwardly by a suitable adjustable spring. Raising of plunger 23 releases latch I 2, 30

raising the press through the pull-back rams. 35

Simultaneously main cylinder. is connected to pump exhaust pipe 2|. Pump pressure is transmittedgthrough a pipe 24 to pilot cylinder 8 for opening filling valve 'I when pump pressure builds up in pipe 20, thereby permitting free flow of a 40 large volume of low pressure liquid from cylinder 4 to the filling tank 6. Inasmuch as the pump and its stroke control are well known devices. detailed description thereof is not deemed necessary.

A particularly desirable improvement of my present invention resides in the following de-- scribed pump control for gradually stopping the platen when it returns to a predetermined top position as well as efiecting a gradually ac- 50 celerated down movement of the .press. This gradual deceleration and acceleration are accomplished by employing a spring 21 for normally biasing the pump to its full stroke position and then controlling a usual pump stroke ad- -initial down movement.

lusting stem 28 in accordance with platen movement through an operative connection therewith. This connection may be by a bellcrank 28 suitably connected through'any necessary links orievels to a rod 30 upon which an adjustable position stop collar II is secured for engagement with any suitable platen abutment 32. With this arrangement it is seen that as the platen moves upwardly, it will engage stop and cause pump control rod 28 to move to the right against the I action of spring 21, thereby gradually reducing the pump stroke until the pump is returned substantially to its neutral position, at which time the press'will stop in its upper position. The pump will remain on a sufficiently short stroke to maintain pressure in the pull-back cylinders for holding up the press. Hence any tendency of the platen to creep or drift downwardly will immediately permit link 30 to move downwardly and accordingly increase the pump stroke so as to supply sufficient fluid to the drawback cylind'ers for restoring the platen to its upper position. The foregoing operation of stopping the platen in its upper position is accomplished without any adjustment of hand lever Ill after its latch i2 is released by the action of pressure responsive plunger 23.

It will be seen that the foregoing pump stroke control also has the advantage that when hand lever II is initially pressed down to shift valve I4 and thereby start the press down, then the pump by already being on short stroke will cause fluid to be gradually withdrawn from the drawback cylinders and thereby permit only a gradual However, the platen movement will be gradually accelerated due to stop I. and link ii moving down with the platen and thus permitting spring -2l,to gradually increase the pump stroke to its full position.

Another arrangement for controlling the pump stroke is to provide, as shown in Fig. 3, the upper end of .rod 2. with a cam 35 which will therefore move vertically in accordance with platen movement and engage the outer end of pump control rod II to adjust-it as in Fig. 1. As-shown in Fig. 4, the accelerating and decelerating functions may be performed and also variable rates of platen movement at any portion of its stroke may be'accornplished by employing a suitably-shaped .cam 30, oscillated or otherwise moved in synchronisni with the platen 2 through any suitable connections to rod ll. Stroke control rod 28 may suitably engage the cam.

In the event of power failure for. the pump a trol valve l4 isin its left hand position while the press is up thus causing pipes l6 and 2. to be in communication with each other. However, re-

verse flow through pipe 2| from the pull-back cylinders is prevented by check valve l'l thereby automatically holding upthe press in the event of power failure.

If it is desired to perform a die setting opera-- tion, the operator would move control valve il in either direction merely by manually raising and lowering hand lever ll without'permitting latch 12 to hold the lever down. .The check valve II will not interfere with this die setting opera- 'tion because the pump would always be discharging in one direction through pipe I.

. Jig. 2 illustrates a-modified arrangement for preventing the press from dropping in' the event of power failure. This means comprises an air operated servo-motor 38 whose piston is secured to the stem of .control valve M and is normally urged in a left direction by a suitable spring. A valve 39 is normally closed by energization of a solenoid 40 connected to a pump motor circuit whereby upon failure of the motor power, solenoid 40 is deenergized to open valve 39 and admit air pressure from anysuitable source Illa through a pipe ll to operate air motor 38 andthus shift stroke for a die setting operation through any suitable link and lever arrangement connected to bellcrank 29, one such connection being diagrammatically' indicated in its simplest form by a ham die 42 directly connected to bellcrank 29, Fig. 2.

It is assumed in the use of hand lever 42 that the pump is adapted to have some degree of reversibility as by shifting the pump on negative stroke such as is possible with'thefI-Iele- Shaw type .of pump. This reversible feature would only be used in connection with the use of the direct die setting control lever such as 42 and even then it is necessary that control valve 14 should be in its left end position so as to connect pipes l6 and" with the pull-back cylinders. Hence it is seen that by moving the pump stroke in one direction or the other from neutral by lever 42, fluid pressure can be alternatively supplied either tothe pull-back cylinders to raise the platen or discharged therefrom to permit the platen to lower. In this operation, check valve I1 is omitted, but nevertheless the press is prevented from falling in the event of power failure by reason of solenoid control 40 and air motor 38 which will return valve It to its neutral position and thus lock pressure in the pull-back cylinders instantly upon power failure.

From the foregoing disclosure it is seen that I have provided means that is particularly effective for automatically controlling press operations such as automatic reversal and stopping of the press at any predetermined top position, as well as eifecting gradual acceleration-in the initial down movement of the platen and gradual deceleration thereof as it approaches its upper position, the gradual acceleration and deceleration being specifically accomplished in an extremely simple manner by short stroking a uni-directionaldiSplacement pump through a direct mechanical connection with the press platen. This particular arrangement in combination with the manually operable reversing valve which permits a unidirectional displacement pump to ,be used for effecting both up and down movements of the press provides an extremely efiective and simple control system while the automatic power control means insures complete safety to the workmen as well as' avoiding possible damage to the dies.

It will'of course be '.nderstood that various changes in details of construction and arrangement of parts may be made by those skilled in the art without departing from the spirit of the invention as set'forth in the appended claim.- 75- I claim:

In combination, a hydraulic press having a platen operated by a main ram and cylinder and a pull-back ram and cylinder, at power driven 5 variable stroke positive displacement pump, a

control valve adapted to distribute fluid from said pump alternatively to said cylinders to eiiect pressing and reversing operations, means for aupump pressure.

tomatically eflectinz and maintoininl short stroking oi said pump in accordance with movement: of the platen when in its returned position there'- by to hold up the platen, end solenoid controlled means tor returning said control valve to its 5 neutral position automatically upon failure of RICHARD W. DINH... 

